Posted
by
timothy
on Tuesday January 12, 2016 @09:35AM
from the graceful-failure dept.

An anonymous reader writes: Scientists have designed a lithium-ion battery that self-regulates according to temperature, to prevent itself from overheating. Reaching extreme temperatures, the battery is able to shut itself down, only restarting once it has cooled. The researchers designed the battery to shut down and restart itself over a repeated heating and cooling cycle, without compromising performance. A polyethylene film is applied to one of the electrodes, which expands and shrinks depending on temperature, to create a conductive/non-conductive material.

No. He means for the scenario where someone makes a statement that is so blatantly wrong that there's no worth in attempting to correct the point of view and just click a couple buttons to mod the ignorance into oblivion.

Of course, we all know that there is no way on this earth that such a mod would be abused in any way./sarcasm

I was thinking the same thing. A passive film won't do a damn thing to stop a short involving a "puncture wound". As pointed out by an earlier poster, most (if not all these days) lithium-ion packs come with one or more a built-in thermistors that inhibits current flow as the battery picks up heat during charging and discharge operations.

You only get rapid heat build up in Li-ion cells if they are gaining or losing charge RAPIDLY. The current safety systems work quite well except where they are not fitted by the battery manufacturer (as is often the case for fast discharge protection) or where the battery is physically damaged (causing a massive short and a circumvention of the safety systems). It is arguably reasonable for a battery manufacturer to leave limiting the discharge rate to the hardware developer because they can't be expected t

You mean "Incorrect". You know moderations are only allowed to start with "in-"You know, to along with our other moderations inconsequential, inflammatory, incongruous, incessant, insightful, interesting, informative, inane, insipid.

If you take apart most Li-Ion battery packs from laptops you will find a thermistor. This is to help prevent the battery from overheating while charging/discharging. Nothing new here except perhaps they are putting them in smaller single cell Li-Ion batteries like cell phone batteries.

If you take apart most Li-Ion battery packs from laptops you will find a thermistor. This is to help prevent the battery from overheating while charging/discharging.

More accurately, it is to help the charger not explode the batteries by charging them too quickly. It's usually used for no other purpose although it's not that unusual for a laptop to tap into it to also report the battery temperature. This is also typically done in power packs for cordless tools. Most of them don't have any kind of over-current protection, though. You can overheat them by misusing the tool, and for the same reason, laptop batteries can combust when one cell goes bad. The idea here is to prevent that by simply shutting off the battery when one cell goes tits up. There's a charge controller in the pack, but there's not a discharge controller.

Well, it's hardly news that Li-ion batteries have a variety of safety features built in. When I was an MIT student back in the 70s Li-ion was exotic tech that you took extreme precautions with. Today Li-ion cells have got so many layers of belts and suspenders it's perfectly safe to be carrying a 3500 mAh battery in your pocket -- as I am dong right now.

But as effective safety measures are, that's not quite the same as having an inherently safe cell. An inherently safe cell could well end up being cheape

Do you say that with a straight face out of ignorance or are you trying to be funny?

The new thing here is that the lithium pack itself becomes self regulating against the problems that can cause them to suddenly bust into flames and not reliant on external circuitry. That is assuming your made in China to a price piece of garbage even has the basic required protection circuits in place. Many don't. But more importantly this would allow for far safer handling of lithium cells themselves. Such things are wide

If you take apart most Li-Ion battery packs from laptops you will find a thermistor. This is to help prevent the battery from overheating while charging/discharging. Nothing new here except perhaps they are putting them in smaller single cell Li-Ion batteries like cell phone batteries.

LiPos have them as well for the same reason.

But this isn't a thermistor that controls a circuit - it's a new cell construction technique that basically has the cell turn itself off when it gets too hot, not externally via a circuit (that may or may not exist, or may be defeated because the Chinese maker of the pack wanted to save a buck).

Yes, counterfeit battery packs exist, and they often are missing the safety circuits as well as using dodgy cells. While there are often very good 3rd party suppliers of battery packs, there are dozens more dodgy sellers of questionable quality 3rd party packs ready and willing to sell you incendiary devices. Probably the reason why those "hoverboards" we see keep catching on fire.

So having the cell be able to protect itself would provide a big increase in safety if you ever find yourself stuck using some crappy quality 3rd party battery packl

It would seem that having the entire battery shut down quickly in response to heat could be a bad thing if you are running only on battery power at that time. Would it be possible to set it up to only shut down some of the battery so that the system could power down safely?

Battery packs are usually wired series parallel in a laptop, so you would see a sudden loss in remaining power rather than a sudden shutdown. For though, it might just power down suddenly unless you have two battery packs in parallel.

Some of us do actual work on laptops. A lot of people are connected via laptop and wireless internet to the office on a nearly 24x7 time frame now. Even when we aren't within range of an internet connection, we still have documents to update; presentations and spreadsheets are still largely a disaster to update on anything smaller than an actual laptop with a physical keyboard.

It would seem that having the entire battery shut down quickly in response to heat could be a bad thing if you are running only on battery power at that time.

Not as bad as having your computer catch fire.

Would it be possible to set it up to only shut down some of the battery so that the system could power down safely?

Maybe. It depends on what kind of voltage monitoring your laptop is doing of your pack. It is technically possible to build per-cell voltage monitoring into the system, and this is in fact not incredibly unusual. Hell, "spare" ADC pins on homebrew "drone" flight controllers are often used for just this purpose — just add a JST-HX connector to your system and you can plug in not just the power connector but also the balanced charging connector and monitor e

Providing it doesn't increase the internal resistance of the battery.Some Li batteries for hobby use are rated to discharge up to 130x their capacity. That's a 5Ah cell discharging 650A.Adding 0.001 ohms to a battery discharging 100A creates an additional 10W of heat. The losses are exponential with current, 200A would result in 40W dissipation.

I have a 14 Ah Li-on whose safety instructions say not to leave it unattended while recharging. That can take up to 16 hrs. What am I supposed to do? Sit in and watch it all day? So I bought an army surplus ammo box to charge it in which I hope would contain any chemical fire. Most of the safety instructions I found on line referred only to the fire risk while recharging, not overheating when on load.

Fire proof bag. I've had 2 batteries catch fire on me. One in a Dell laptop, the other was an unprotected lithium cell hooked to an expensive charger and charging in a flame proof bag. Both were charging cases but the problem can occur during any high temperature scenario including a short circuit on an unprotected cell.

well - both charging and dis-charging (using them) can trigger the same event. If you draw enough current the battery will get hot - normally the circuit breaker (if you have one) will pop/burn. I believe most Li-on fires are runaway due to impurities or defects in the battery itself. Once they get hot enough they can't stop - kind of a melt down.

A friend of mine has model aircraft that run on batteries - he charges them in a giant tin-can outdoors. He once had one catch fire while charging (guess it go

The trouble is how to define "full" it's a moving target that changes with ambient temperature, battery age etc. You can count coulombs as you put them into the battery (which costs you some of them of course) and you can report on how many of them depart as you discharge, but no system is 100% efficient and the charge and discharge rates are also non-linear so you always "seems" to put in more than you get out and during continuous current draw by the system the output voltage of the battery fluctuates in

Thanks for the explanation. Sounds like plenty of failure mode analysis in your system.

I should also point out that he was purchasing unprotected battery cells simply wrapped in a rubber like material - cheap on the internet shipped from an unknown location in China;-) These batteries felt like a block of clay - and he was putting them in a model airplane with only the airframe & velcro protecting them from damage.

Talk about risk taking. We'd all mock-hide when it became obvious he was about to "aug

A runaway LiIon is not just a "fire". There can be violent outgassing and blowtorching. If you try to hermetically close the ammo box while charging, it could easily be blown apart and imitate a grenade. If you DON'T seal it, the gas and flames could be voluminously emitted from the container.

I would think a fireplace would be far safer. If you don't have one, mabe you could stack a labyrinth of firebricks on a big metal base. If the weather is nice and you have a sandy or gravelly or paved driveway with pl

Recently mother, extremely unnerved, called me - claiming her dog brought a dud firework home and it exploded, nearly causing a fire.

Later it was revealed it was not a firework. The dog stole a Li-Ion battery for my phone from my room. Biting into it shorted it, and the battery exploded hard, shooting ribbons of burning lithium all around like a true firework.

I wonder when these will go into mass production. Obviously, there are "hover" boards exploding to be concerned about, but there was a plane crash [wikipedia.org] attributed to these, and that's always good to avoid.